State transitions in cyanobacteria studied with picosecond fluorescence at room temperature

Ahmad Farhan Bhatti, Reza Ranjbar Choubeh, Diana Kirilovsky, Emilie Wientjes, Herbert van Amerongen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Cyanobacteria can rapidly regulate the relative activity of their photosynthetic complexes photosystem I and II (PSI and PSII) in response to changes in the illumination conditions. This process is known as state transitions. If PSI is preferentially excited, they go to state I whereas state II is induced either after preferential excitation of PSII or after dark adaptation. Different underlying mechanisms have been proposed in literature, in particular i) reversible shuttling of the external antenna complexes, the phycobilisomes, between PSI and PSII, ii) reversible spillover of excitation energy from PSII to PSI, iii) a combination of both and, iv) increased excited-state quenching of the PSII core in state II. Here we investigated wild-type and mutant strains of Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 using time-resolved fluorescence spectroscopy at room temperature. Our observations support model iv, meaning that increased excited-state quenching of the PSII core occurs in state II thereby balancing the photochemistry of photosystems I and II.

Original languageEnglish
Article number148255
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1861
Issue number10
DOIs
Publication statusPublished - 1 Oct 2020

Keywords

  • Cyanobacteria
  • Excited-state quenching
  • State transition
  • Time-resolved spectroscopy

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